[the_pwner224]

Yes. Everything "just works" and it's quite easy to add block rules in the Fastmail web interface.

You initially set up the wildcard alias: for any email to *@example.com, route it to [e-mail]

Then you can add rules to drop emails to [e-mail], [e-mail], .... Those work independently from the wildcard.

[beeboop]

i guess im very pedantic - i don't want to make a rule to delete a email. i want it to bounce and never see my inbox and have the sender see that it bounced.

[mttjj]

Fastmail has first-class support for exactly what you want. Settings > Users & Aliases > + New Alias > "Show advanced preferences". There's a checkbox that says "Disable - Reject (bounce) all mail sent to this address (disable the alias) Disable a specific address when you have a wildcard (catch-all) alias."

[beeboop]

thanks - i didn't realize i could make an alias after the fact and then disable. appreciate it!